Hopefully we haven't lost anyone. It's hard to judge so I've taken to over-explaining, especially on how the idea of inertia is tied to everything when it comes to space and time. We'll double down on inertia when it comes to gravity. Inertia never happens to you, it's a thing that you see happening to everyone else and yet everyone is correct and they'd argue it never happens to them either. It's a point of view and the universe respects that.

It's like it's built out of maths, something muzzy strongly disagrees with.

There's a chance we will never know how it all works.  Our ability may be limited by the logical and mathematical systems we work in. We may be incapable of working with the systems that are required to figure it all out because of how we perceive the world or the plane of existence we are on.  

Godel found out that our systems are flawed and maybe that is a fundamental limit showing itself to us.

Maybe we will one day build something that can think in the way that is required but if we do maybe we won't understand it when it tries to explain it to us.

Doesn't mean we can't keep striving though. Never say never.  We need to figure out how to travel off this planet in the meantime.

I'm not sure AI which is still based on stuff we already know will make any sort of breakthrough.

If AI or we do figure it out that may well reveal how we get off the planet.

A theory of everything could well be very simple when looked at by a higher level of intelligence than we have. We are rats measuring the maze and what it's made of without any idea of what's outside it.

If we don't figure it all out then we might be able to terraform instead of finding somewhere the same as here. That is more likely to succeed. We could move outward in our solar system before our sun becomes a red giant which would buy us more time.

With you on our greed based stupidity though.  We don't plan anywhere near far enough ahead to do anything of consequence.  We need to think of doing really big things in a different way because we shackle our efforts by trying to pay for things with money which is only an imaginary thing anyhow.

We should stop trying to break the planet as for now (forever?) it is our only home.

Imagine there is a fair amount of crossover between the two goals.

Ok, so we have Einstein arguing that all inertial frames really are equal and there's no background space that defines a true speed. This means that all the equations of physics must be valid in all inertial frames - that the equals sign holds, and that includes Maxwell's. Before Maxwell, physics hadn't properly investigated electric charge/magnetism and was more or less about stuff moving and Newton's laws of motion.

If we observe a physics lab on a train, people appreciated you couldn't really tell that you were moving when you did your motion experiments on the train because the lab was moving along with the physicist (because of inertia) and it gave the illusion, at least to the physicist, that they weren't moving. People really thought it was an illusion the physicist suffered from. But now we had all this charge and magnetism stuff and light popping out of it, and everyone but Einstein assumed these phenomena would break on a moving train/spaceship. If the speed of light was a constant it better bloody well be a constant relative to some other universal constant, and everyone assumed that was absolute space.

Start thinking that speed is a purely relative concept leads to all sorts of disconcerting thoughts because speed = dist / time, and no physicist was prepared to think they were relative too. They didn't even think about thinking about it. There were a couple of brave mathematicians, notably Lorentz, but no proper scientists believed those fannies anyway. Just because they'd proved that the speed of light is independent from the source by only using a pen and paper didn't mean anything. Frankly, they were getting a bit above their station and they should knuckle down and do actual experiments like real men.

But in 1905 Einstein didn't care. He wasn't in academia because nobody would have him. He passed his exams but after graduation he couldn't pursue his dream of physics research. Staring into space during lectures and thinking about ground breaking ideas can sometimes give the impression you're a bit of a dimwit, and people thought he was either lazy or stupid. Luckily for us he was forced to take a really boring job at a Swiss patent office. Thank fuck they didn't have the internet back then and his mind was free to wander without doing any experiments. Thought experiments were enough despite what physicists with beards say. So boring was it that all the ideas he'd built up over the years formulated into several but distinct physics-shattering ideas.

And the one we're concerned about is Maxwell and inertia. Inertia is only a different perception of distance. As per the vid that Liv posted, Jim doesn't see a distance that the audience does because they perceive him as moving and Jim doesn't. For Jim, the light clock is just moving up and down. The audience sees a saw-tooth pattern because relative to them Jim is moving horizontally.

But crucially, according to Einstein they all see the speed of the beam (c) moving at the same speed. This would not apply if Jim was bouncing a basketball. The audience would see the ball moving faster because they have to add the up and down movement to the horizontal movement they see Jim moving. But if Einstein is right, they both see the path of the beam going at the same speed when it comes to light because that must be a constant in all inertial frames, and both Jim and the audience are.

So it's the observed distance of the path of the light we have to account for. Jim sees a smaller distance than the audience do but everyone agrees the light is moving at c.

So what's going on? If speed = dist/ time, then c = dist / time, for the audience and Jim. 

But if the LHS of the equation is a constant for Jim and the audience (c), yet they both see different distances, we must realise they both experience different times to make the LHS a constant for both parties! Jim and the audience do not agree on what the clock says because they don't agree on the distance the light has traveled.

With the basketball they don't agree with the distance either but that's fine because they don't agree on the speed, so they're happy to agree the LHS is different and the time part can stay the same for both.

That's the thought experiment? It's almost like...... too simple?

double forum borked post

This is the part to think deeply about.

SpaceGazelle wrote:

So the speed of a torch moving relative to Einstein doesn't come into it. And if Einstein is right then the light is not moving relative to space either. Light is invariant to all motion.

Ah ok. in that context the ramifications make more sense. Einstein was the first one to consider c a constant.

We need to combine space and time into spacetime and it'll start to become clearer.

So the conclusion to all of this is that you can't move relative to anything that's moving at the speed of light. Hang on you might say, I can move towards a light beam. The fucker's moving towards me! But you actually can't. If you could you would observe it as coming towards you faster. You can move towards the Sun but you cannot move to towards the light itself. The gap between you and the light beam is merely a point of view and the bias in your inertial frame interprets this as movement.

That’s pretty much were I am too. I read through and go ‘Yep. Got it.’ But then five minutes later I need to read it over again.

Accepting but not understanding. I need to spend a little time with it before I’ll cross that barrier. But that’s how I always feel about physics stuff.

What about Doppler shift tho eh?